I'm trying to construct a name in Scots Gaelic meaning "Devotee of Lugh." Would I be correct in thinking Maollugh or Maellugh would be appropriate? I know maol & mael usually translates into "servant of," is there a better word I should use?

Mael/Maol literally means "bald" but can be used also in the sense of "follower of" /"devotee of" from an ancient custom of tonsured hair worn by people following a certain spiritual tradition eg. tonsures were worn by druids and later by early Christian followers of saints in Ireland and presumably in other Celtic regions where Christianity had been imported (but a different pattern of tonsure was worn by druids and early priests/monks). The tonsure signified their religious path and so seeing someone with head shaven in a particular tonsure would identify this "bald" person as a "follower of" X or Y. After the introduction of Christianity to Ireland, there seems to have been some taboo about directly adopting religious names of saints as personal names (much as in the way nowadays in the English-speaking world, it would be rare to call someone Jesus but it is common in Spanish-speaking areas) and so the prefix Mael- was added to the adopted name to enable it to be used. This is common in the formation of surnames from around about the late 900s onwards. Other prefixes were also used, eg. mac 'son of', ui/O "Grandson of"/"from" (should be lengthmarks on the i of ui and the O but I can't do them on this computer)', Giolla (earlier gilla) 'servant of' / 'messenger of', etc. This is how surnames like GillaPatraic (Giollapadraig) derive - "servant of Patrick", etc.

So yes, use prefixes like Gilla (mod Ir Giolla), Mael (mod. Maol), Mac, Ceile ('companion of', length mark on first e) etc. to denote "follower of". The name following is usually in the genitive (possessive case) to create the "of X" translation, so I guess it would be Mael-Loga in your case if you are using it for Lug (Lugh). Mael Brigte for "follower of Brigit (Brighid) etc.

I should clarify that I am giving you Old Irish (to about late 800s) and Modern Irish above, not Scots Gaelic, but as Scots Gaelic derives from Old Irish, it should be in the same vein.
regards
Beith